Implementation of null-aware operators.

pkg/compiler/lib/src/resolution/semantic_visitor.dart

 // Copyright (c) 2015, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library dart2js.semantics_visitor;
 
 import '../constants/expressions.dart';
 import '../dart2jslib.dart' show invariant, MessageKind;
 import '../dart_types.dart';
 import '../elements/elements.dart';
@@ skipping 286 matching lines @@
   ///
   /// For instance
   ///     m(receiver) => receiver.foo;
   ///
   R visitDynamicPropertyGet(
       Send node,
       Node receiver,
       Selector selector,
       A arg);
 
+  /// Conditional (if not null) getter call on [receiver] of the property
+  /// defined by [selector].
+  ///
+  /// For instance
+  ///     m(receiver) => receiver?.foo;
+  ///
+  R visitIfNotNullDynamicPropertyGet(
+      Send node,
+      Node receiver,
+      Selector selector,
+      A arg);
+
   /// Setter call on [receiver] with argument [rhs] of the property defined by
   /// [selector].
   ///
   /// For instance
   ///     m(receiver) {
   ///       receiver.foo = rhs;
   ///     }
   ///
   R visitDynamicPropertySet(
       SendSet node,
       Node receiver,
       Selector selector,
       Node rhs,
       A arg);
 
+  /// Conditional (if not null) setter call on [receiver] with argument [rhs] of
+  /// the property defined by [selector].
+  ///
+  /// For instance
+  ///     m(receiver) {
+  ///       receiver?.foo = rhs;
+  ///     }
+  ///
+  R visitIfNotNullDynamicPropertySet(
+      SendSet node,
+      Node receiver,
+      Selector selector,
+      Node rhs,
+      A arg);
+
   /// Invocation of the property defined by [selector] on [receiver] with
   /// [arguments].
   ///
   /// For instance
   ///     m(receiver) {
   ///       receiver.foo(null, 42);
   ///     }
   ///
   R visitDynamicPropertyInvoke(
       Send node,
       Node receiver,
       NodeList arguments,
       Selector selector,
       A arg);
 
+  /// Conditinal invocation of the property defined by [selector] on [receiver]
+  /// with [arguments], if [receiver] is not null.
+  ///
+  /// For instance
+  ///     m(receiver) {
+  ///       receiver?.foo(null, 42);
+  ///     }
+  ///
+  R visitIfNotNullDynamicPropertyInvoke(
+      Send node,
+      Node receiver,
+      NodeList arguments,
+      Selector selector,
+      A arg);
+
   /// Getter call on `this` of the property defined by [selector].
   ///
   /// For instance
   ///     class C {
   ///       m() => this.foo;
   ///     }
   ///
   /// or
   ///
   ///     class C {
@@ skipping 1273 matching lines @@
   ///       m() => super[1] = 42;
   ///     }
   ///
   R visitUnresolvedSuperIndexSet(
       Send node,
       Element element,
       Node index,
       Node rhs,
       A arg);
 
+  /// If-null, ??, expression with operands [left] and [right].
+  ///
+  /// For instance
+  ///     m() => left ?? right;
+  ///
+  R visitIfNull(
+      Send node,
+      Node left,
+      Node right,
+      A arg);
+
   /// Logical and, &&, expression with operands [left] and [right].
   ///
   /// For instance
   ///     m() => left && right;
   ///
   R visitLogicalAnd(
       Send node,
       Node left,
       Node right,
       A arg);
@@ skipping 55 matching lines @@
   R visitDynamicPropertyCompound(
       Send node,
       Node receiver,
       AssignmentOperator operator,
       Node rhs,
       Selector getterSelector,
       Selector setterSelector,
       A arg);
 
   /// Compound assignment expression of [rhs] with [operator] of the property on
+  /// a possibly null [receiver] whose getter and setter are defined by
+  /// [getterSelector] and [setterSelector], respectively.
+  ///
+  /// For instance:
+  ///     m(receiver, rhs) => receiver?.foo += rhs;
+  ///
+  R visitIfNotNullDynamicPropertyCompound(
+      Send node,
+      Node receiver,
+      AssignmentOperator operator,
+      Node rhs,
+      Selector getterSelector,
+      Selector setterSelector,
+      A arg);
+
+  /// Compound assignment expression of [rhs] with [operator] of the property on
   /// `this` whose getter and setter are defined by [getterSelector] and
   /// [setterSelector], respectively.
   ///
   /// For instance:
   ///     class C {
   ///       m(rhs) => this.foo += rhs;
   ///     }
   /// or
   ///     class C {
   ///       m(rhs) => foo += rhs;
@@ skipping 663 matching lines @@
   ///     m(receiver) => ++receiver.foo;
   ///
   R visitDynamicPropertyPrefix(
       Send node,
       Node receiver,
       IncDecOperator operator,
       Selector getterSelector,
       Selector setterSelector,
       A arg);
 
+  /// Prefix expression with [operator] of the property on a possibly null
+  /// [receiver] whose getter and setter are defined by [getterSelector] and
+  /// [setterSelector], respectively.
+  ///
+  /// For instance:
+  ///     m(receiver) => ++receiver?.foo;
+  ///
+  R visitIfNotNullDynamicPropertyPrefix(
+      Send node,
+      Node receiver,
+      IncDecOperator operator,
+      Selector getterSelector,
+      Selector setterSelector,
+      A arg);
+
   /// Prefix expression with [operator] on a [parameter].
   ///
   /// For instance:
   ///     m(parameter) => ++parameter;
   ///
   R visitParameterPrefix(
       Send node,
       ParameterElement parameter,
       IncDecOperator operator,
       A arg);
@@ skipping 421 matching lines @@
   ///     m(receiver) => receiver.foo++;
   ///
   R visitDynamicPropertyPostfix(
       Send node,
       Node receiver,
       IncDecOperator operator,
       Selector getterSelector,
       Selector setterSelector,
       A arg);
 
+  /// Postfix expression with [operator] of the property on a possibly null
+  /// [receiver] whose getter and setter are defined by [getterSelector] and
+  /// [setterSelector], respectively.
+  ///
+  /// For instance:
+  ///     m(receiver) => receiver?.foo++;
+  ///
+  R visitIfNotNullDynamicPropertyPostfix(
+      Send node,
+      Node receiver,
+      IncDecOperator operator,
+      Selector getterSelector,
+      Selector setterSelector,
+      A arg);
+
   /// Postfix expression with [operator] on a [parameter].
   ///
   /// For instance:
   ///     m(parameter) => parameter++;
   ///
   R visitParameterPostfix(
       Send node,
       ParameterElement parameter,
       IncDecOperator operator,
       A arg);
@@ skipping 442 matching lines @@
   ///
   /// For instance
   ///     class C {}
   ///     m1() => unresolved;
   ///     m2() => prefix.unresolved;
   ///     m3() => Unresolved.foo;
   ///     m4() => unresolved.foo;
   ///     m5() => unresolved.Foo.bar;
   ///     m6() => C.unresolved;
   ///     m7() => prefix.C.unresolved;
+  ///     m8() => prefix?.unresolved;
+  ///     m9() => Unresolved?.foo;
+  ///     m10() => unresolved?.foo;
+  ///     m11() => unresolved?.Foo?.bar;
   ///
   // TODO(johnniwinther): Split the cases in which a prefix is resolved.
   R visitUnresolvedGet(
       Send node,
       Element element,
       A arg);
 
   /// Read of the unresolved super [element].
   ///
   /// For instance
@@ skipping 11 matching lines @@
   ///
   /// For instance
   ///     class C {}
   ///     m1() => unresolved = 42;
   ///     m2() => prefix.unresolved = 42;
   ///     m3() => Unresolved.foo = 42;
   ///     m4() => unresolved.foo = 42;
   ///     m5() => unresolved.Foo.bar = 42;
   ///     m6() => C.unresolved = 42;
   ///     m7() => prefix.C.unresolved = 42;
+  ///     m8() => prefix?.unresolved = 42;
+  ///     m9() => Unresolved?.foo = 42;
+  ///     m10() => unresolved?.foo = 42;
+  ///     m11() => unresolved?.Foo?.bar = 42;
   ///
   // TODO(johnniwinther): Split the cases in which a prefix is resolved.
   R visitUnresolvedSet(
       Send node,
       Element element,
       Node rhs,
       A arg);
 
   /// Invocation of the unresolved [element] with [arguments].
   ///
   /// For instance
   ///     class C {}
   ///     m1() => unresolved(null, 42);
   ///     m2() => prefix.unresolved(null, 42);
   ///     m3() => Unresolved.foo(null, 42);
   ///     m4() => unresolved.foo(null, 42);
   ///     m5() => unresolved.Foo.bar(null, 42);
   ///     m6() => C.unresolved(null, 42);
   ///     m7() => prefix.C.unresolved(null, 42);
+  ///     m8() => prefix?.unresolved(null, 42);
+  ///     m9() => Unresolved?.foo(null, 42);
+  ///     m10() => unresolved?.foo(null, 42);
+  ///     m11() => unresolved?.Foo?.bar(null, 42);
   ///
   // TODO(johnniwinther): Split the cases in which a prefix is resolved.
   R visitUnresolvedInvoke(
       Send node,
       Element element,
       NodeList arguments,
       Selector selector,
       A arg);
 
   /// Invocation of the unresolved super [element] with [arguments].
@@ skipping 95 matching lines @@
   ///
   /// For instance
   ///     class C {}
   ///     m1() => unresolved += 42;
   ///     m2() => prefix.unresolved += 42;
   ///     m3() => Unresolved.foo += 42;
   ///     m4() => unresolved.foo += 42;
   ///     m5() => unresolved.Foo.bar += 42;
   ///     m6() => C.unresolved += 42;
   ///     m7() => prefix.C.unresolved += 42;
+  ///     m8() => prefix?.unresolved += 42;
+  ///     m9() => Unresolved?.foo += 42;
+  ///     m10() => unresolved?.foo += 42;
+  ///     m11() => unresolved?.Foo?.bar += 42;
   ///
   // TODO(johnniwinther): Split the cases in which a prefix is resolved.
   R visitUnresolvedCompound(
       Send node,
       Element element,
       AssignmentOperator operator,
       Node rhs,
       A arg);
 
   /// Prefix operation of [operator] reading from the non-existing static getter
@@ skipping 90 matching lines @@
   ///
   /// For instance
   ///     class C {}
   ///     m1() => ++unresolved;
   ///     m2() => ++prefix.unresolved;
   ///     m3() => ++Unresolved.foo;
   ///     m4() => ++unresolved.foo;
   ///     m5() => ++unresolved.Foo.bar;
   ///     m6() => ++C.unresolved;
   ///     m7() => ++prefix.C.unresolved;
+  ///     m8() => ++prefix?.unresolved;
+  ///     m9() => ++Unresolved?.foo;
+  ///     m10() => ++unresolved?.foo;
+  ///     m11() => ++unresolved?.Foo?.bar;
   ///
   // TODO(johnniwinther): Split the cases in which a prefix is resolved.
   R visitUnresolvedPrefix(
       Send node,
       Element element,
       IncDecOperator operator,
       A arg);
 
   /// Postfix operation of [operator] reading from the non-existing static
   /// getter and writing to the static [setter].
@@ skipping 89 matching lines @@
   ///
   /// For instance
   ///     class C {}
   ///     m1() => unresolved++;
   ///     m2() => prefix.unresolved++;
   ///     m3() => Unresolved.foo++;
   ///     m4() => unresolved.foo++;
   ///     m5() => unresolved.Foo.bar++;
   ///     m6() => C.unresolved++;
   ///     m7() => prefix.C.unresolved++;
+  ///     m8() => prefix?.unresolved++;
+  ///     m9() => Unresolved?.foo++;
+  ///     m10() => unresolved?.foo++;
+  ///     m11() => unresolved?.Foo?.bar++;
   ///
   // TODO(johnniwinther): Split the cases in which a prefix is resolved.
   R visitUnresolvedPostfix(
       Send node,
       Element element,
       IncDecOperator operator,
       A arg);
 
   /// Invocation of an undefined unary [operator] on [expression].
   R errorUndefinedUnaryExpression(
@@ skipping 736 matching lines @@
   ///       C() : this._(42);
   ///     }
   ///
   R errorUnresolvedThisConstructorInvoke(
       Send node,
       Element element,
       NodeList arguments,
       Selector selector,
       A arg);
 }